Sky Lights: Lunar Wink, Cosmic Candle, and Mars
The grizzled wizards of yore who peeped and muttered might have peered at the night skies this week and thrown fits.
With a comet growing brighter in the predawn and early evening skies, a lunar eclipse due this weekend, and Mars at its biggest and brightest, they might have recommended that their king duck under the bed and stay put for a few days.
These days, however, such events - especially the arrival of comet Hale-Bopp - are eliciting more "oohs" than "uh-ohs." Astronomers are pulling out all the stops to probe the comet's secrets. And people all over are pulling out their wallets to buy binoculars and telescopes to watch the celestial display.
The boom in business "has really taken us by surprise," says Farah Payan, a saleswoman at Woodland Hills Camera in Woodland Hills, Calif. "We've got a lot of first-time buyers or people buying accessories to take pictures. Telescope sales are up about six times over what they typically are without a major event like this."
Little wonder, since people are being treated to what some hail as the second "great" comet in a year - a designation given only to the best and the brightest. On average, only three or four comets a century are bright enough for the general public to see, says Karen Meech, an astronomy professor at the University of Hawaii.
Visible in the northeastern US before dawn and the Northwest at twilight, Hale Bopp is a naked-eye object even for people living in the glow of urban lights. In areas with darker skies it is visually richer, since more of the lighter dust tail and the bluish tail of ionized gas are visible.
Last year's comet, Hyakutake, "was especially interesting to the public because it came so close to Earth," says Dr. Meech. "But its output of dust and gas is nothing compared with Hale-Bopp. This is a truly extraordinary comet." Like other comets, Hale-Bopp is composed of ice and dust thought to be left over from the primeval nebula that gave birth to the solar system.
And like other comets, Hale-Bopp is full of surprises. Take ethane, for example, first discovered on Hyakutake. Significant amounts also have appeared on Hale-Bopp. That such a "warm" gas formed on objects that dwell at the coldest reaches of the solar system begs a question, Meech says: "Do we really understand how comets form, or do we really understand interstellar chemistry?"
Scientists will have a chance to struggle with these questions at an international forum on the comet, scheduled for early next February.
For all its exotic flair, the comet isn't the only astronomical display on this week's schedule. On March 23, much of the Western Hemisphere will be treated to its last major lunar eclipse this century. Between 8:41 p.m. and 9:20 p.m. Eastern time, the full moon should begin to darken as it enters Earth's shadow. By 11:39 p.m., 92 percent of the moon will take on an eerie reddish cast, leaving a white "cap" where 8 percent avoids the darkest part of the shadow. People east of the Rockies will get the best show. Although "you can't get chump change" to study eclipses anymore, according to an astronomer acquaintance, they make useful teaching tools and give the public a high-profile show on a cloudless night.
Meanwhile, Mars makes its closest and brightest approach to Earth this week, making it a prominent target not just for professional and amateur telescopes - it also gives engineers planning Mars missions something to shoot at. Last December, NASA launched two unmanned missions - Mars Global Surveyor and Mars Pathfinder - to the Red Planet, using Mars's relatively close position to cut fuel costs and speed their arrival. Mars Pathfinder is scheduled to land on July 4.